Once upon a time, the mantra of "build quality sites and links will happen naturally" actually had some basis in fact. Those days are long gone, and anyone who still spouts that is on holidays from Xanadu. Link acquisition has become one of the most contrived, polluted, untruthful and downright dishonest parts of web development you will ever come across.
Ever noticed how may posters in here, and on other forums, say they have given up on link building, or send their link building offshore. Some are turning to social media in hopes that they are somehow going to stumble on the next magic bullet.
All this comes about because Google's success has turned links into the currency of the web development marketplace. The never ending efforts of SEO "specialists" fill our inboxes, trying to entice the gullible into hopelessly irrelevant link swaps.
We are beseeched to buy links from the Acme Link Selling Corp who's slogan is "Google Will Never Know". We are asked to sell links for use on websites who promise "we'll Never Share Your Ugly Secret". We see large families of sites that interlnk the bejesus out of each other in hopes of gaming Googles SERP's. Whether that works or not is not the point, it's yet another sign that links do not happen naturally and some folks will do whatever it takes to create link affluence.
In the minds of most web developers, Page Rank and Trust Rank came to symbolize link success and acceptance into the Google fold. By linking to other sites there is a perception that you are somehow giving away some of your affluence so it doesn't happen. Be honest, how many of you with successful sites are still actively involved in link exchanges with start-up sites?
So as more and more start-up websites keep bursting forth into the web environment, there is a dwindling number of links (and sources of links) that will do those sites any good in Google's eyes. So the older, established sites start to become the holders of all primary currency that Google recognizes.
How long can Google keep generating the best SERP's if the indicators that it relies on become less and less and the natural competition between sites becomes more stifled?